OU - Denotes Origin Unknown


New surveys require the setting of legal iron bars on boundary corners with the surveyor's official number that is inscribed near the top of the iron bar. Over time, however, the surveyor number may fade or rust away and can no longer be read. It is customary to mark such legal monument or any other type of found marker as "OU" or origin unknown, if the actual monument origin cannot be determined from field inspection or other documentary research (some surveyors use "NI" or Not Identified). The actual physical location of the found iron bar, iron pipe, cut arrow or even "car axle" may still be the best evidence of the location of the boundary or corner, despite the uncertain monument origin. Before accepting this physical evidence, however, the surveyor must research and confirm it corresponds and supports dimensions and bearings/directions found in other documentary evidence such as deeds, field notes, survey plans or registered/reference plans.


Identifies that the origin of a found legal survey monument is uncertain.

Why is this important?

Iron bars or other physical evidence found at property corners are typically the best evidence of the boundary. OU is a designation used by surveyors when the bar's identification number is not readable or when we cannot identify the origin of an old rusty pipe found at property corner.